Identifying anniversaries to celebrate is not exactly the most pressing issue facing the scientific community these days.

There’s much more important stuff. Like articulating the seriousness of climate change and searching for new knowledge that will aid in combatting it. Or coping with sexual harassment and discrimination. Or securing reliable funding from a nonfunctioning government. Not to mention figuring out what dark matter is.

Still, maintaining sanity requires occasional diversion from all the sources of darkness, despair and despondency. In bleak days it sometimes helps to recall happier moments and reflect on some of science’s great accomplishments and the scientists responsible for them. Fortunately 2019 offers numerous opportunities for celebration, many more than can fit in a Top 10. So don’t be dismayed if your favorite isn’t listed (such as J. Presper Eckert’s centennial, John Couch Adams’ or Jean Foucault’s 200th birthday or Caroline Furness’ 150th).

10. Andrea Cesalpino, 500th birthday

Unless you are an exceptionally serious botany fan, you’ve probably never heard of Cesalpino, born June 6, 1519. He was a physician, philosopher and botanist at the University of Pisa until the pope, in need of a good doctor, called him to Rome. As a medical researcher Cesalpino studied the blood and had some sense about its circulation long before the English physician William Harvey figured out the big blood picture. Cesalpino was most impressive as a botanist, generally credited with writing the first botany textbook. He didn’t get everything right, of course, but he described many plants accurately and classified them more systematically than previous researchers, who mostly regarded plants as a source for medicines. Today his name is memorialized by the flowering plant genus Caesalpinia.

9. Leonardo da Vinci, 500th anniversary of death

Less than a month before Cesalpino was born, Leonardo died, on May 2, 1519. Leonardo is much more famous in the popular mind as an artist than a scientist, but he was also a serious anatomist, geologist, engineer and mathematician (hello, Renaissance man). His role in the history of science was limited because so many of his ingenious ideas resided in notebooks that nobody read until long after his death. But he was a prolific and imaginative observer of the world. He developed elaborate geological views on river valleys and mountains (he thought the peaks of the Alps had once been islands in a higher ocean). As an engineer, he recognized that complex machines combined a few simple mechanical principles, and he insisted on the impossibility of perpetual motion. He formulated basic ideas about work, power and force that became cornerstones of modern physics when developed more precisely by Galileo and others more than a century later. And of course, Leonardo probably would have invented the airplane if he had sufficient funding.

8. Petrus Peregrinus’ treatise on magnetism, 750th anniversary

Magnetism had been known since ancient times, as a property exhibited by certain iron-containing rocks known as lodestones. But nobody understood very much about it until Petrus Peregrinus (or Peter the Pilgrim) came along in the 13th century. He left behind very few clues about his personal life; nobody knows when he was born or died. But he must have been a profoundly talented mathematician and technician, praised profusely by the famously critical natural philosopher Roger Bacon (if the Peter he referred to was actually the Pilgrim).

In any case, Peter composed the first substantial scientific treatise on magnetism (completed August 8, 1269), explaining the concept of magnetic poles. He even realized that if you broke a magnet into pieces, each piece became a new magnet with its own two poles — north and south, in analogy with the poles of the “celestial sphere” that supposedly carried the stars around the Earth. But Peter did not realize that compasses worked because the Earth itself is a giant magnet. Nor did he anticipate the laws of thermodynamics, designing what he thought was a magnetism-powered perpetual motion machine. Leonardo would have recommended against giving it a patent.

7. Magellan’s circumnavigation of the globe, 500th anniversary

On September 20, 1519, Ferdinand Magellan set sail from southern Spain with five ships on a transoceanic trek that would require three years to circumnavigate the globe. But Magellan made it only halfway, killed in a skirmish in the Philippines. Still, the voyage retains his name, although some modern sources prefer to call it the Magellan-Elcano expedition to include Juan Sebastián Elcano, commander of the Victoria, the only ship of the original five to make it back to Spain. Historian Samuel Eliot Morison noted that Elcano “finished the navigation, but he was only carrying out Magellan’s plan.”

Among the great navigators of the Age of Discovery, Morison opined, “Magellan stands supreme,” and because of his contributions to navigation and geography, “the scientific value of this voyage is beyond doubt.” Although it certainly wasn’t necessary to sail around the Earth to prove that it was round, circumnavigating the globe for the first time surely qualifies as a significant human achievement, even if ranking slightly behind going to the moon.

6. Moon landing, 50th anniversary

Apollo 11 was mainly a symbolic (though technically difficult) achievement, but nevertheless scientifically significant. Besides boosting the science of lunar geology by bringing back moon rocks, the Apollo astronauts deployed experiments to measure moonquakes (thereby learning more about the moon’s interior), studied the lunar soils and the solar wind, and left behind a mirror as a target for Earth-based lasers to measure the distance to the moon with high precision. (Later Apollo missions deployed more extensive experiments as well.)

But even more than providing new scientific results, the Apollo mission represented a celebration of past scientific achievements — the understanding of the laws of motion and gravity and chemistry and propulsion (not to mention electromagnetic communication) —accumulated by earlier scientists who had no idea that their work would someday make Neil Armstrong famous.

5. Alexander von Humboldt, 250th birthday

Born in Berlin on September 14, 1769, von Humboldt was perhaps the 19th century’s best candidate for the designation of Renaissance man. Not only a geographer, geologist, botanist and engineer, he was also a world-class explorer and one the most important writers of popular science of his century. With the botanist Aimé Bonpland, von Humboldt spent five years scouring South America and Mexico for new plants while also recording 23 volumes’ worth of observations on geology and minerals, meteorology and climate, and other geophysical data. He was both a deep and broad thinker, composing a five-volume work called Cosmos that essentially conveyed the totality of modern (as it was then) science to the general public. And he was also one of science’s leading humanitarians, arguing vigorously in opposition to slavery, racism and anti-Semitism.

4. Thomas Young’s paper on measurement error, bicentennial

An Englishman famous for an experiment showing the wave nature of light, Young was also a physician and linguist. This year’s anniversary celebration recognizes one of his more obscure papers, published two centuries ago (January 1819), on the math related to the probability of errors in scientific measurements. He commented on the use of probability theory to express the reliability of experimental results in “a numerical form.” He found it interesting to show why “the combination of a multitude of independent sources of error” has a natural tendency “to diminish the aggregate variation of their joint effect.” In other words, if you make a lot of measurements, the size of the probable error of your result will be smaller than if you make just one measurement. And math can be applied to estimate the probable size of the error.

Young warned, though, that such methods could be misused: “This calculation has sometimes vainly endeavoured to substitute arithmetic for common sense,” he pointed out. It’s necessary to guard against any “constant causes of errors” (now known as “systematic errors”) in addition to random error. And he noted that it is “very seldom safe to rely on the total absence of such causes,” especially when the “observations are made by any one instrument, or even by any one observer.” Trust in math without concern for such considerations, he warned, could lead to erroneous conclusions: “For want of considering this necessary condition, the results of many elegant and refined investigations, relating to the probabilities of error, may in the end be found perfectly nugatory.” So there.

3. Johannes Kepler’s Harmonices Mundi, 400th anniversary

Kepler, one of the greatest physicist-astronomers of the 17th century, attempted to reconcile the ancient idea of the harmony of the spheres with the modern astronomy that he had helped to establish. The original idea, attributed to the Greek philosopher-mathematician Pythagoras, was that spheres carrying the heavenly bodies around the Earth generated a musical harmony. Apparently nobody heard this music because, some Pythagoreans contended, it was present at birth and so was unnoticed background noise.

Kepler believed the construction of the universe, with the sun rather than Earth at its center, observed harmonious mathematical ratios. He had long sought to explain the architecture of the solar system as corresponding to nested geometrical solids, thereby prescribing the distances separating the (elliptical) planetary orbits. In Harmonices Mundi (Harmony of the World), published in 1619, he admitted that solids alone could not accurately account for the details of planetary orbits — additional principles were needed. Most of his book is no longer relevant to astronomy, but its lasting contribution was Kepler’s third law of planetary motion, which showed the mathematical relationship between a planet’s distance from the sun and the time the planet takes to complete one orbit.

2. Eclipse expedition validates Einstein, centennial

Albert Einstein’s general theory of relativity, completed in 1915, predicted that light from a distant star passing near the sun would be bent by the sun’s gravity, altering the apparent position of the star in the sky. Newtonian physics could explain some such bending, but only half as much as Einstein had calculated. Observing such light seemed like a good way to test Einstein’s theory, except for the slight problem that you can’t see stars at all when the sun is in the sky. Both Newtonian and Einsteinian physics agreed, though, on when the next solar eclipse would be, making stars near the edge of the sun briefly visible.

British astrophysicist Arthur Eddington led an expedition to observe an eclipse from an island off the coast of West Africa in May 1919. Eddington found that deviations for some stars from their previously recorded location matched general relativity’s forecast close enough to declare Einstein the winner. Apart from making Einstein famous, the result didn’t matter much at the time (apart from encouraging general relativity’s use in theorizing about cosmology). But general relativity became a big deal decades later, when it was needed to explain new astrophysical phenomena and also to make it possible for GPS devices to be accurate enough to do away with road maps.

1. Periodic Table! Sesquicentennial!

Dmitrii Mendeleev was not the first chemist to notice that several groups of elements had similar properties. But in 1869 he identified a guiding principle for classifying the elements: If you list them in order of increasing atomic weight, elements with similar properties recur at regular (periodic) intervals. Using this insight he created the first periodic table of the elements, one of the grandest accomplishments in the history of chemistry. Many of science’s great achievements appeared in the form of inscrutable mathematical formulas, or required elaborate experiments requiring intuitive genius, great manual dexterity, enormous cost or complex technology.

But the periodic table is a wall chart. It allows anybody to grasp at a glance the foundations of an entire scientific discipline. Mendeleev’s table has often been reconstructed, and its guiding rule is now atomic number rather than atomic weight. But it remains the most versatile consolidation of profound scientific information ever constructed — an iconic representation of all the types of matter from which earthly substances are made. And you can find it not only on classroom walls, but also on ties, T-shirts and coffee mugs. Someday maybe it will decorate the walls of a chemistry-themed restaurant — called The Periodic Tables.